Pipe stressing programs will often show that the selected class of flange is not capable of accommodating the applied piping moments. In this case, unless a higher class of flange is chosen or the piping layout changed to reduce the flange moments, the pipe stressing program will indicate that the piping does not meet all of the requirements of the piping code. If the moments acting on the flange cannot be reduced, must a higher class of flange be chosen or are there other flange analysis techniques that can be used to show that the moments are not excessive? This paper compares a range of flange analysis techniques to investigate the bending moments that may be accommodated; both from a flange stress and from a flange leakage point of view. The objective of the work is to illustrate the variations in computed results and to help the piping designer choose an appropriate method for assessing flange moments. There is a multitude of different flange configurations considering combinations of flange type, size, class, schedule, gasket and the results of any comparison will be affected by many other parameters such as pressure, temperature and bolt pretension. The comparisons have thus been limited to a range of commonly used flange configurations in sizes up to 12 inch in an attempt to draw some general conclusions about the various assessment methods.

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